To understand how a virus works, it is necessary to think on very small scales. At a so small scale that the human eye could never see the movements of a virus. In fact, viruses are tiny microbes on the planet, yet they can make a person sick and even kill.
Then, the questions are: How can something so small make a person so sick? How does a virus reproduce inside the body until it infects another person? Can we avoid getting sick in the presence of a virus?
They are more common than you think
The first thing you should know about viruses is that they are small pieces of RNA (ribonucleic acid) or DNA (deoxyribonucleic acid), wrapped up in a layer of proteins, which protect their genetic material. This means that they cannot replicate on their own, so they need a host cell to be able to live.
They come in very different shapes: as rods, rounds, with crowns or cylindrical tails. However, it is not possible to see this with a simple microscope. To see a virus, it is necessary to use a scanning electron microscope, which uses electrons instead of light to produce an image.
Another important fact is that there are many types of viruses. Some can just cause a common flu, while others can be more harmful such as HIV, Ebola or Coronavirus. And, there are viruses that enter the human body, but the immune system manages to fight them, so the person does not get sick.
In short, viruses can replicate and create other viruses. This is possible as they can adapt very easily to any environment and any host. They are made to survive very difficult conditions.
How do they enter the body?
Usually these microorganisms enter the body through the mouth, eyes, nose, genitals or through wounds, bites or any open wounds. Moreover, they are transmitted through different routes.
Some diseases are spread by direct contact with infected skin, mucous membranes or body fluids. There is also the possibility of indirect contact, when a person touches an object (door, handle, table), which has the virus on it, when an infected person sneezes, coughs or talks or when the mucous membrane comes into contact with another person.
In some other cases, the virus is transmitted through common vehicle such as contaminated food, water or blood. Finally, there are vectors: rats, snakes, mosquitoes etc., which transmit the virus to humans.
The virus inside the human body
These organisms enter the body and adhere to the cell surface. Depending on the type of virus, it seeks for cells in different parts of the body: liver, respiratory system or blood. Once it has attached itself to the healthy cell, it enters it.
When the virus is inside the cell, it will open up so that its DNA and RNA will come out and go straight to the nucleus. They will enter a molecule, which is like a factory, and make copies of the virus. These copies will come out of the nucleus to be assembled and receive protein, which protects their DNA and RNA.
These new copies of the virus (millions of copies) will leave the already infected cell to infect other healthy cells, where they will multiply again. Infected cells can be damaged or die while hosting a virus.
It is important to clarify that when a virus infects a human, it does not always end up in a disease. The infection occurs when the virus begins to multiply. And, the disease occurs when many body cells are damaged by the infection, which is also when the symptoms and illness appear.
In a nutshell, if the immune system manages to fight off the virus that entered the cells and replicated, the person will not get sick. Nevertheless, the body will respond in different ways to fight these foreign bodies.
When the immune system fails to control the virus, a process called pathogenesis begins. The virus crosses obstacles such as distance, the immune system or mucous membranes to reach different organs.
Once it begins to replicate, the person will get sick and his/her organs will be infected. Depending on how severe the symptoms are, the person will have to rest or seek medical help.
How to fight the virus?
The immune system is the body’s first line of defense. If it is not able to fight the virus because it has already infected several organs, a treatment can be used to relieve the symptoms (inflammation of the organs that produces cough, headache, etc.), until the immune system is able to defend the body.
Likewise, drugs, such as antivirals, may be used as they get inside the cells and are integrated into the genomes of the virus to stop it from replicating. This means that antivirals damage the virus DNA chains in order to prevent them from working. Therefore, these drugs are used to fight viruses such as herpes or hepatitis C.
On the other hand, viruses can be prevented with vaccines. Nowadays, this is the most efficient approach used. The vaccine produces a specific immunity against a disease because it trains antibodies and cells to recognize the infectious agent.
In conclusion, viruses are microorganisms that can only live if they find a host. Once they find it, if they manage to overcome all natural and scientific barriers that the body produces, they can infect the person. Plus, if they manage to overcome the immune system, the person will get sick.
Although it is impossible to prevent any virus from infecting humans, through the experience of generations and the help of science, the human body should be able to defend itself from foreign agents.